Motor cooling apparatus



Nov. 19, 1968 1 A R. SMITH ET AL 3,411,320

MOTOR COOLING APPARATUS Filed Sept. 9, 1966 United States Patent O 3,411,320 MOTOR COOLING APPARATUS Lewis R. Smith, Edwin I. Ghormley, and Robert C. Hartman, Dayton, Ohio, assignors to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Sept. 9, 1966, Ser. No. 578,250 13 Claims. (Cl. 62-505) ABSTRACT F THE DISCLOSURE Refrigerating apparatus including a condenser, an evaporator, and a compressor connected together to form a closed refrigerant system with an electric motor drivingly connected to the compressor. An .equalizer line extends from the evaporator below the level of liquid refrigerant in the latter to a sump located in the refrigerant line between the condenser and the evaporator. A take-olf line extends from the sump to the electric motor for delivering liquid refrigerant from the sump to the electric motor.

This invention relates to motor cooling apparatus, and more particularly to apparatus for cooling the motor of the motor driven compressor assembly of a refrigeration system having a closed refrigerant circuit.

There are several known methods of cooling the motor of the compressor assembly of a centrifugal refrigeration system. In some systems liquid refrigerant is expanded into the motor for cooling it by evaporation of the refrigerant. The refrigerant for cooling the motor is normally drawn off from the refrigerant cycle and then returned to the latter after effecting cooling of the motor. Usually, the condenser of the refrigeration system is mounted at a higher elevation than the evaporator so that during shutdown 'of the system, when the pressures in the compressor equalize, lthe liquid refrigerant in the condenser or condenser sump will drain, by the force'of gravity, into the evaporator. This occurs because the evaporator is often at a lower temperature than the condenser when the system is not operating. With the evaporator and condenser at an equalized pressure, the liquid refrigerant will tend to accumulate in the coldest part of the system, i.e., the evaporator. When the motor is energized, and during its initial starting operations, there is little or no liquid refrigerant in the bottom of the condenser, or condenser sump for cooling the motor.

Some of the known refrigeration systems provide one or more liquid refrigerant pumps for pumping refrigerant from the evaporator or a sump attached to the evaporator to the motor driving the compressor during starting operations of the motor. The utilization of such pumps, with the accompanying electrical controls and circuitry, not only add to the cost of manufacture of such systems, but also increase the services which must be rendered to maintain the refrigeration system in proper operational condition. Moreover, safety devices are normally added to the refrigeration system to sense the failure of the pump or ypumps so that the electric motor for driving the compressor will not be damaged if the pump or pumps should fail.

Accordingly, it is a primary object of this invention to provide motor cooling apparatus for cooling the motor of the motor driven compressor of a refrigeration system wherein liquid refrigerant is supplied to the motor during start-up conditions without employing a pump, thereby insuring adequate cooling of the motor without the maintenance, safety and other problems encountered when a pump is used to supply liquid refrigerant during start-up or running conditions.

Another object of this invention is to provide motor ice cooling apparatus of the class described in which liquid refrigerant is delivered from the evaporator to a sump or reservoir for insuring an adequate supply of liquid refrigerant when the motor is energized.

Still another object of this invention is to provide refrigeration apparatus having a motor driven compressor unit mounted in such manner relative to the evaporator and condenser units that vibration normally accompany the operation of such a compressor and transmitted to the remaining equipment is substantially reduced.

A further object of this invention is to provide motor cooling apparatus such as described which is substantially automatic in operation.

Another object of this invention is to provide motor cooling apparatus of the type described which is simple and economical in construction, and effective in operation.

Other objects and features of this invention will become apparent as the description progresses.

In the accompanying drawings, in which one of various possible embodiments of this invention is illustrated,

FIG. 1 is a diagrammatic illustration of the motor cooling apparatus of this invention; and

FIG. 2 is a diagrammatic view showing the relative positions between various parts of the apparatus.

Like parts are indicated by corresponding reference characters in both views of the drawings.

Referring now to the drawings, the motor cooling apparatus lof this invention is generally indicated at 1 in FIG. 1. The refrigeration system which includes the motor cooling apparatus basically comprises a centrifugal or other type of compressor 3 driven by an electric motor 5, a condenser 7 connected to the compressor and adapted to receive refrigerant vapor from it, and an evaporator or cooler 9 connected to the compressor 3 for supplying refrigerant vapor to it.

The condenser 7 may be of shell type in which cooling fluid, such as water, flows through tubing 11 for cooling and condensing refrigerant vapor entering into the condenser 7 through an inlet 13. The evaporator 9 may also be of the shell type and has tubes 15 carrying the liqiud to be cooled, such as water or brine for example, therein. The liquid in tubes 15 circulates between the evaporator 9 and the cooling load served by the refrigeration apparatus to transfer heat from the load to the evaporator. In transferring this heat to the evaporator, the refrigerant in the evaporator outside tubes 15 boils and forms vapor which may pass through a liquid eliminator 17 and through an outlet 19 to the compressor 3.

The condenser 7 and evaporator 9 are mounted in sideby-side relation with the weight of compressor 3 and its driving motor 5 located above and between the two heat exchanging units 7 and 9. The location of the compressor and motor weight in the center of the two heat exchanger units 7 and 9, as diagramatically illustrated in FIG. 2, has a dampening effect on the vibratory characteristics of the apparatus.

A discharge conduit 20 is connected to an outlet 21 located in the lower side of condenser 7 and extends from condenser 7 to a condenser sump or header 23. A liquid refrigerant take-off line or delivery tube 25 extends from a point adjacent the bottom of sump 23 to a lter drier 27. Another tube 29 extends fromiilter drier 27 to motor 5 through branches 29a and 29b. Refrigerant from the sump is forced, by the difference in pressure between that in the condenser and that in the evaporator, from the sump 23 through line 25, lter drier 27, line 29, the motor windings and rotor in the motor and a line 31 to the evaporator. The refrigerant leaves the sump as a liqiud and vaporizes progressively as the pressure is reduced and as heat is added to it from the motor.

The line 31 is connected to the evaporator 9 at a point below the eliminator 17. The refrigerant, as it leaves the motor, will be mostly in the vapor phase. However, some liquid, not evaporated, may also be flowing through line 31 to the evaporator. The vapor portion mixes with other vapor generated in the evaporator by heat transfer and flows through the elminator 17 and outlet 19 to the compressor. Any liquid refrigerant not evaporated mixes with the liquid being evaporated in the evaporator. i

It will be understood that only a relatively small amount of refrigerant need be supplied for the refrigeration of motor 5. Most of the liquid refrigerant discharged from condenser 7 will be delivered to the evaporator 9. This is accomplished by means of a transfer conduit or line 33 extending from the upper portion of sump 23 to the bottom of evaporator 9 below a distributor plate 35. The amount of liquid refrigerant delivered from sump 23 to evaporator 9 through line 33 is controlled by a liquid control valve 37 which is operated by an electric motor 38 in response to the operation of a float switch 39. Switch 39 is operated by a float 41 having a switch actuating rod 43 connected thereto and extending upwardly from the sump 23 through a guide tube 45. The motor operated liquid control valve 37 functions as a high-side float expansion valve type control and prevents partial flooding of the condenser which frequently occurs in refrigeration systems having a fixed orifice in the line connecting the condenser to the evaporator. rThe utilization of the motorized valve 37 also avoids the seating problems which are associated with many refrigeration systems having a mechanically-operated float valve in the line joining the condenser to the evaporator.

To assure an adequate supply of liquid refrigerant in the condenser sump 23 after the refrigeration apparatus has been shut down and prior to start-up an equalizer line 47 extends from the evaporator 9 in the lower portion thereof to the sump 23. The equalizer line 47 is relatively small in diameter so that there is no adverse efect on the refrigeration system during operation of the latter by the small amount of liquid refrigerant which is carried from the sump 23 to the evaporator 9 around -the valve controlled line 33. However, if desired, a check valve may be placed in line 47 to prevent the flow of liquid refrigerant from sump 23 to evaporator 9 during normal operating conditions.

Operation of the apparatus of this invention is as follows:

During normal operation of the refrigeration apparatus, the refrigerant is circulated through the refrigeration cycle by the pressure difference created by the compressor. The vapor from the compressor is delivered to the condenser 7 at which point the Vapor is condensed to liquid by the cooling tubes 11. The liquid refrigerant is discharged from the lower side of condenser 7 through the discharge conduit to sump 23. From the sump, most of the liquid refrigerant flows through transfer line 33 to the bottom of evaporator 9. The amount of liquid passing through line 33 to evaporator 9 is dependent upon the operation of float switch 39 and motor operated liquid control valve 37. However, since the lower end of takeoff or delivery line is below the inlet of line 33, liquid refrigerant due to pressure difference, flows through line 25, filter drier 27, and line 29 to the motor 5 for cooling purposes. Most of the liquid refrigerant substantially vaporizes in the motor as the latter is cooled and the refrigerant vapor is returned to the refrigeration cycle through line 31.

The amount of liquid refrigerant supplied to motor 5 is equal to or greater than the actual quantity required for motor cooling. Any excess liquid refrigerant not evaporated in the motor returns to the evaporator through line 31 with the evaporized refrigerant.

As set forth previously, a small amount of the liquid refrigerant from sump 23 would flow to the evaporator 9 through line 47 if line 47 did not contain a check valve.

However, this small amount of liquid refrigerant will usually not adversely affect the refrigeration cycle.

When the motor 5 is de-energized, the pressures in the centrifugal compressor 3 driven by a motor 5 will soon equalize throughout the stages thereof. The liquid refrigerant in the various conduits and pipes of the motor cooling apparatus drains, due to the force of gravity, to the lower parts of the system. The liquid refrigerant also tends to accumulate in the coolest part of the system, usually the evaporator. Since equalizer line 47 connects the lower portion of evaporator 9 to sump 23, the liquid levels in the evaporator and sump-condenser unit 23 and 21 tend to equalize. This assures an adequate liquid supply in the sump 23 for cooling the motor during start-up of the latter. Moreover, an adequate supply of liquid refrigerant still remains in the evaporator so that during start-up of the motor 5 and compressor 3 the refrigerant pressure and corresponding saturated refrigerant temperature are prevented from becoming too low during the transient starting period.

After the motor has attained running speed and is operating under normal conditions, the amount of liquid in the condenser 7 and sump 23 is controlled by the float switch 39 and valve 37. At this point, the bulk of the liquid refrigerant is located in the evaporator 9.

A motor cooling system constructed in accordance with this invention was built and tested. During the tests, a sight glass was installed in the take-off or delivery line 25. During start up, liquid refrigerant was observed flowing to the motor in approximately six seconds after the motor was energized and before it had reached full speed. During the entire testing period, the motor windings never lacked refrigerant for cooling and the winding temperatures were always safely below critical values for the insulation system.

It will be noted that the lower portion of condenser 7, conduit 20, sump 23, line 33 and valve 37 form passage means for delivering refrigerent from the condenser to the evaporator, while line 25, lter drier 27, and line 29 form passage means for delivering refrigerant to the motor 5. Equalizer line 47 forms another refrigerant carrying passage means for delivering refrigerant from the evaporator to the sump. The elevation of the inlet of line 25 is below the elevation of the inlet of line 33 so that the lattter cannot withdraw all of the refrigerant from the sump and must leave a supply of refrigerant for motor 5.

It will thus be seen that the motor cooling apparatus of this invention is adapted to provide an adequate liquid refrigerant supply at start-up without the use of a separate liquid pump, thus eliminating the potential maintenance and failure problems associated with systems utilizing separate refrigerant pumps. Moreover, by locating the motor and compressor weight above and between the evaporator and condenser the vibration normally associated with the apparatus of centrifugal refrigeration systems is reduced.

In view of the foregoing, it will be seen that the several objects of this invention are achieved.

It will be understood that the invention is not to be limited to the exact constructions shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

We claim:

1. In a refrigeration system having a refrigerant condenser, a refrigerant evaporator, a compressor for withdrawing refrigerant from said evaporator and delivering refrigerant from said evaporator and delivering refrigerant to said condenser, an electric motor connected to said compressor for driving the latter, first passage means connecting said condenser to said evaporator, second passage means connecting said evaporator to said compressor, third passage means connecting said compressor to said condenser, said passage means cooperating with said condenser, evaporator and compressor to provide a closed circuit for refrigerant, fourth passage means having an inlet in communication with said first passage means, said fourth passage means having at least one outlet connected to said motor for delivering refrigerant to the latter, fifth passage means for returning refrigerant from said motor to the circuit, sixth passage means having an inlet connected to said evaporator and an outlet in communication with said first passage means, said sixth passage means being adapted to deliver refrigerant from said evaporator to said first passage means when said motor is de-energized and the level of liquid refrigerant in said evaporator is higher than the level of liquid refrigerant in said first passage means adjacent said fourth passage means inlet, said first passage means including a sump for holding a supply of refrigerant, and first and second portions connected to said sump, said first portion extending from said condenser to said sump and said second portion extending from one elevation in said sump to said evaporator, said fourth passage means inlet being located at a second elevation in said sump lower than said first elevation to assure a supply of refrigerant for cooling said motor during operation of said refrigeration system.

2. In a refrigeration system as set forth in claim 1 further comprising a valve in said second portion of said first passage means, and means for operating said valve in response to the changes in the level of the refrigerant in said sump.

3. In a refrigeration system as set forth in claim 2 wherein said means for operating said valve comprises power means for opening and closing said valve, a switch for controlling the operation of said power means, a float in said sump, and means connecting said float to said switch for actuating the latter in response to the changes in the level of the refrigerant in said sump.

4. In a refrigeration system as set forth in claim 1 wherein said evaporator and condenser are mounted in side-by-side relation, and said motor and compressor are mounted above and between said evaporator and condenser.

5. In a refrigeration system having an evaporator, a condenser, a motor, and a compressor driven by said motor, first refrigerant carrying means connecting said condenser to said evaporator, second refrigerant carrying means connecting said evaporator to said compressor, third refrigerant carrying means connecting said cornpressor to said condenser, said refrigerant carrying means cooperating with said condenser, evaporator and compressor to provide a closed refrigerant circuit, and means for cooling the motor driving said compressor; said means for cooling the motor comprising a liquid refrigerant carrying line for delivering liquid refrigerant to the motor, said line having an inlet end in said first refrigerant carrying means and extending to said motor, a return refrigerant line for returning refrigerant from said motor to the circuit, and means for delivering liquid refrigerant from said evaporator to said first refrigerant carrying means at a point adjacent the inlet end of said liquid refrigerant carrying line for returning liquid refrigerant to the first refrigerant carrying means prior to start-up of the motor and when the level of liquid refrigerant in the evaporator is at a higher elevation than the level of liquid refrigerant in said first refrigerant carrying means adjacent the inlet end of said liquid refrigerant carrying line.

6. In a refrigeration system as set forth in claim 5 further comprising valve means in said first refrigerant carrying means between said sump and said evaporator, erant carrying line and said evaporator, and means for controlling the operation of said valve means in response to the level of liquid refrigerant in said first refrigerant carrying means adjacent the inlet end of said liquid refrigerant carrying line.

7. In a refrigeration system as set forth in claim 5 wherein said first refrigerant carrying means includes a sump for holding a supply of refrigerant, said inlet end of said liquid refrigerant carrying line being located in said sump.

8. In a refrigeration system as set forth in claim 7 further comprising valve means in said first refrigerant carrying means between said sump and said evaporator, and means for controlling the operation of said valve means in response to the level of liquid refrigerant in said sump.

9. In a refrigeration system having a refrigerant condenser, a refrigerant evaporator, a refrigerant compressor, an electric motor connected to said compressor for driv ing the latter, a first refrigerant carrying passage connecting said condenser to said evaporator, a second refrigerant carrying passage connecting said evaporator to said compressor, a third refrigerant carrying passage co-nnecting said compressor to said condenser, said passages cooperating with said condenser, evaporator and cornpressor to provide a closed refrigerant circuit, said first passage having a sump therein for holding a supply of refrigerant, one portion of said first passage having an inlet in the upper portion of said sump and extending from the latter to said evaporator, a motor refrigerant carrying line extending from said sump to said motor for delivering refrigerant to the latter, said line having an inlet end located below the inlet of said one portion of said first passage, a return line for returning refrigerant from said motor to the circuit, and an equalizer line connecting the lower portion of said evaporator to said sump, said sump being |located at approximately the same level as the lower portion of said evaporator, whereby said equalizer line returns refrigerant from said evaporator to said sump when said motor is de-energized and the level of the refrigerant in said evaporator is higher than the level of the refrigerant in said sump.

10. In a refrigeration system as set forth in claim 9 wherein said evaporator and said condenser are mounted in side-byside relation at approximately the same level for facilitating the return of refrigerant from said evaporator to said sump and condenser through said equalizer line, and said motor and compressor are mounted above and between said evaporator and condenser.

11. In a refrigeration system as set forth in claim 9 further comprising a valve for controlling the flow of refrigerant through said one portion of said first passage, and means responsive to the level of refrigerant in said sump for operating said valve.

12. In a refrigeration system as set forth in claim 11 wherein said means for operating said valve comprises power means for opening and closing' said valve, a switch for controlling the operation of said power means, a fioat in said sump, and means connecting said fioat to said switch for actuating the latter in response to the changes in the level of the refrigerant in said sump.

13. In a refrigeration system as set forth in claim 12 wherein said evaporator and said condenser are mounted in side-by-side relation at approximately the same level for facilitating the return of refrigerant from said evaporator to said sump and condenser through said equalizer line, and said motor and compressor are mounted above and between said evaporator and condenser.

References Cited UNITED STATES PATENTS 3,022,638 2/ 1962 Caswell et al. 62-115 3,232,074 2/ 1966 Weller et al. 62--505 3,270,521 9/1966 Rayner et al 62--84 ROBERT A. OLEARY, Primary Examiner. 

